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authorLibravatar Martin Ågren <martin.agren@gmail.com>2018-05-20 12:50:32 +0200
committerLibravatar Junio C Hamano <gitster@pobox.com>2018-05-21 13:58:32 +0900
commit17154b1576f8be5aa3044f3adadb5473da618a42 (patch)
tree38f1785f400756a59acc50c78755f78ef1be0a89 /diffcore-order.c
parentGit 2.17 (diff)
downloadtgif-17154b1576f8be5aa3044f3adadb5473da618a42.tar.xz
regex: do not call `regfree()` if compilation fails
It is apparently undefined behavior to call `regfree()` on a regex where `regcomp()` failed. The language in [1] is a bit muddy, at least to me, but the clearest hint is this (`preg` is the `regex_t *`): Upon successful completion, the regcomp() function shall return 0. Otherwise, it shall return an integer value indicating an error as described in <regex.h>, and the content of preg is undefined. Funnily enough, there is also the `regerror()` function which should be given a pointer to such a "failed" `regex_t` -- the content of which would supposedly be undefined -- and which may investigate it to come up with a detailed error message. In any case, the example in that document shows how `regfree()` is not called after `regcomp()` fails. We have quite a few users of this API and most get this right. These three users do not. Several implementations can handle this just fine [2] and these code paths supposedly have not wreaked havoc or we'd have heard about it. (These are all in code paths where git got bad input and is just about to die anyway.) But let's just avoid the issue altogether. [1] http://pubs.opengroup.org/onlinepubs/9699919799/functions/regcomp.html [2] https://www.redhat.com/archives/libvir-list/2013-September/msg00262.html Researched-by: Eric Sunshine <sunshine@sunshineco.com> Signed-off-byi Martin Ågren <martin.agren@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
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